One of the most controversial issues in Sacramento this year has been what is widely referred to as the “sanctuary state” law, which will take effect Jan. 1.

It is intended to protect law-abiding immigrants from being set on a path toward deportation after interactions with local police. But in immigrant communities and elsewhere, there is confusion about how the law will work—and exactly what protection it provides.

Gov. Jerry Brown signed the measure, named the California Values Act, into law after negotiations made it more palatable to law enforcers, who had protested it initially.

Why do people call it the “sanctuary state” law when the senator who wrote it says the phrase is a misnomer?

The author, state Senate leader Kevin de Léon, a Los Angeles Democrat, and others say the label is confusing, because the term “sanctuary” has become political—a flashpoint in the immigration debate.

The phrase originated with people who took sanctuary in churches. Some undocumented immigrants continue to do so, and so far, immigration officials have not gone to places of worship to arrest them. However, just being in California does not mean immigrants have blanket protection from federal authorities. The state law sets up guidelines for California law enforcement agencies’ interactions with federal immigration authorities. Undocumented immigrants may still face deportation if they have committed crimes or are swept up in raids by federal agents at workplaces, in neighborhoods or other venues, or if they are arrested individually.

The Values Act has been called a tool for public safety, put in place to ensure that immigrants continue to feel safe cooperating with local police as reporters of crimes and witnesses in court. Some police officials, including the chief of police in Los Angeles, endorsed the law for this reason.

What does the new law actually do?

The measure erects a barrier between state/local law enforcement, and federal immigration agencies. It doesn’t completely prohibit cooperation or the transfer of certain felons to federal custody; it creates a framework for when state agencies may cooperate with federal agencies. Previously, state and local authorities could use their discretion in many circumstances.

For people convicted of certain crimes—as many as 800, identified in a 2013 law called the Trust Act—there is little protection. Those infractions range from violent crimes and other serious offenses to felony drunk driving. State and local police agencies will still be allowed to let federal immigration authorities know when individuals are to be released, and to hand them over to those agents. However, individuals cannot be held beyond their release dates even if they have committed serious crimes.

The law also allows state corrections officials to continue to work with federal immigration agencies regarding those who are incarcerated and who face deportation after serving their sentences. They will continue to communicate with federal authorities about who is in prison and their expected release dates, and will hand those individuals over to federal agents upon release.

But the new law prohibits new or expanded contracts between the federal government and local facilities to be used as detention centers. Existing contracts are allowed to continue. The law also designates all courts, schools, libraries and hospitals as safe zones—immune to immigration enforcement as long as federal law does not require arrests there.

Police and sheriff’s deputies will not be allowed to act as immigration authorities; inquire about a person’s immigration status; detain someone based only on a federal hold request; participate in arrests based on immigration status; assist immigration authorities in arrests; or transfer people to federal custody without a warrant or certain other criteria.

Does the Values Act mean immigration agents can’t deport people in California?

No. No one can claim that living in California makes them exempt from deportation. Federal authorities can conduct raids, arrest suspected undocumented immigrants and do other work separately from state and local law enforcement. In addition, they can continue to communicate with local agencies about arrestees who have committed certain crimes, and they will be able to take custody of those individuals from local lockups when they are released. Agencies, however, will not honor “hold requests” from federal immigration agencies that previously could last up to 48 hours.

Does it mean undocumented immigrants won’t be deported if they commit violent crimes?

No. Immigrants—those here both legally and illegally—are not safe from deportation under the new law. Undocumented immigrants who are convicted of certain crimes will continue to be reported to federal immigration officials for deportation. The list of relevant crimes was not included when the Values Act was originally proposed. However, Gov. Jerry Brown negotiated with de León to ensure that those who commit serious crimes—including homicide, sexual assault and theft—will not be allowed to stay, while those arrested for a minor offense will not be held for deportation.

What will happen if a county or city does not follow the new law and allows its authorities to cooperate with immigration agents?

Local agencies that do not follow the new law could face lawsuits by advocacy groups or others for failing to uphold it, or for constitutional claims such as wrongful detention. They could also face action from the state attorney general. Some law-enforcement groups that had criticized the measure dropped their opposition when the list of excluded crimes in the new law was increased from 60 to 800.